The petrographic and petrologic observations made in this study support the following model. The large-scale submarine volcanism documented across the Pacific at ~120 Ma is now suggested to have affected the Shatsky Rise as well. On the Shatsky Rise, there is a pulse of ash input just prior to the deposition of the OAE1a interval. Its alteration makes its origin somewhat indeterminable; it may have been a direct product of OJP eruptions or, more likely, an indirect product via reactivation of the older volcanic edifices on the rise. Intrusion-related uplift associated with this magmatic rejuvenation may account for the pre-OAE1a submarine unconformities at Sites 1213 and 1214 on the Southern High. Alternatively, the hiatus/unconformity could have been produced by scouring of the ridge by deep ocean currents or an impact-related tsunami. There is no evidence for subaerial exposure. Very poor recovery across this interval precludes a more detailed analysis. As suggested by several workers (e.g., Leckie et al., 2002; Larson and Erba, 1999) this Pacific-wide period of submarine volcanism likely increased productivity via iron fertilization. Higher productivity led to enhanced accumulation of organic matter. The organic-rich interval was widespread and developed bacterial mats. Eventually, these volcanic centers built up above sea level, evolving into subaerial volcanoes. Emergence cut off the source of iron, and productivity dramatically declined. The exposed volcanic highs and associated shallow shelf areas then shed a mix of hydroclastic (blocky), epiclastic, and glauconitic debris into deeper water. The epiclastic debris is mostly microlitic and locally tachylitic, suggesting that source lavas cooled slowly, as would be expected in a subaerial setting. Rounding of the epiclastic debris is consistent with transport in a beach setting or possibly a high-energy shelf. The glauconite is a diagenetic replacement of the volcanic debris after it was carried out onto the adjacent shelf. No shallow-water bioclastic debris was observed in these units, but this may be a diagenetic overprint. Alternatively, the "young" island volcanoes may not have had time to develop reef systems. The time frame involved with this interval (tuffaceous and organic-rich intervals) is relatively short, on the order of 1 m.y., which would be consistent with the time frame needed for the rejuvenation and then subsidence of the volcanic centers. This story, although best told through the stratigraphic section on the Shatsky Rise, is also represented in the Mid-Pacific Mountains at Site 463.